The invention relates to a method of heating a glass sheet for tempering. It comprises conveying the glass sheet on top of rollers in a roller-hearth furnace, heating the glass sheet in the roller-hearth furnace to a transfer temperature at which the glass sheet is transferred into an air support furnace. The glass sheet, while resting on an air cushion, is carried on an air support table and the glass sheet is heated in the air support furnace to a tempering temperature. The transfer temperature is not lower than 620 C. and not higher than 675 C. and the tempering temperature is not lower than 650 C. and not higher than 720 C.

The invention relates to a method of heating a glass sheet for tempering. It comprises conveying the glass sheet on top of rollers in a roller-hearth furnace, heating the glass sheet in the roller-hearth furnace to a transfer temperature at which the glass sheet is transferred into an air support furnace. The glass sheet, while resting on an air cushion, is carried on an air support table and the glass sheet is heated in the air support furnace to a tempering temperature. The transfer temperature is not lower than 620 C. and not higher than 675 C. and the tempering temperature is not lower than 650 C. and not higher than 720 C.

A strengthened cover glass or glass-ceramic sheet or article as well as processes and systems for making the strengthened glass or glass-ceramic sheet or article is provided for use in consumer electronic devices. The process comprises cooling the cover glass sheet by non-contact thermal conduction for sufficiently long to fix a surface compression and central tension of the sheet. The process results in thermally strengthened cover glass sheets for use in or on consumer electronic products.

A strengthened cover glass or glass-ceramic sheet or article as well as processes and systems for making the strengthened glass or glass-ceramic sheet or article is provided for use in consumer electronic devices. The process comprises cooling the cover glass sheet by non-contact thermal conduction for sufficiently long to fix a surface compression and central tension of the sheet. The process results in thermally strengthened cover glass sheets for use in or on consumer electronic products.

A strengthened cover glass or glass-ceramic sheet or article as well as processes and systems for making the strengthened glass or glass-ceramic sheet or article is provided for use in consumer electronic devices. The process comprises cooling the cover glass sheet by non-contact thermal conduction for sufficiently long to fix a surface compression and central tension of the sheet. The process results in thermally strengthened cover glass sheets for use in or on consumer electronic products.

A strengthened cover glass or glass-ceramic sheet or article as well as processes and systems for making the strengthened glass or glass-ceramic sheet or article is provided for use in consumer electronic devices. The process comprises cooling the cover glass sheet by non-contact thermal conduction for sufficiently long to fix a surface compression and central tension of the sheet. The process results in thermally strengthened cover glass sheets for use in or on consumer electronic products.